This project is meant to provide an understanding of factors that influence the development of proximal tubule amino acid recovery. The beta-amino acid, taurine, will be used as a model transport probe since it has insignificant renal metabolism, is not incorporated into protein and defines the beta-amino system. Moreover taurine appears to be an important amino acid for the development of the central nervous system in human neonates. Studies of its renal reabsorption during development are therefore of importance. The urinary excretion of taurine will be measured in immature and adult rats. Using thin cortex slices (3-5 mg) the kinetics of uptake and efflux will be compared in tissues from rats of different ages, as well as the influence of medium sodium, anoxia, and glutathione oxidizing agents. The transport of taurine into isolated membrane preparations, both the brush border and lateral-basal membrane, will be compared at various ages. The transport of taurine will also be compared to that of another beta-alanine, and 2 - alpha amino acids, alpha-AIB and alpha Alanine. Once the age related patterns of transport into cortex slices and membrane vesicles are known, the effects of various agents such as parathyroid hormone, dibutyryl cyclic AMP, cyclic AMP, increased amounts of amino acid in the diet or reduction of litter size to increase nutrient supply will be assessed on these age related changes. These studies should indicate whether induction or derepression is the mechanism responsible for the ontogenic emergence of specific transport proteins.